Series-Tuned Amplifier, a Low Noise Preamplifier

Parallel-tuned circuits are commonly used in transistor bandpass amplifiers, e.g., IF amplifiers. However, series-tuned circuits have some important advantages. This correspondence presents a simple noise analysis for a parallel-tuned and a series-tuned amplifier. The transfer functions of both amplifiers are similar, but the series-tuned amplifier gives a smaller noise figure. Hence, series-tuned circuits are especially advantageous in preamplifiers.